Recommended Online PC games

Ok so I am looking for good multiplayer online games that are on PC.

Currently the only ones that I regularly play multiplayer online are:
Counterstrike: Source
Starcraft
Unreal Tournament 3

The thing is it seems that no one on this forum has any of those games except for Starcraft.
I know multiplayer generally means online nowadays but ... my major emphasis about online is that it won't require a significant amount of magic to get it to work over the internet.

So what other games do people play or would recommend that are playable: on PC, multiplayer, online, preferably free?

most mmorpgs are free..but guess you don't like them judging from the currently playe ones